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If y ≠ 3 and 3x/y is a prime integer greater than 2, which of the following must be true? Ⅰ. x = yⅡ. y = 1Ⅲ. x and y are prime integers.(A) None(B) Ⅰ only(C) Ⅱonly(D) Ⅲonly(E) Ⅰand Ⅲ

Guys, I am sure this might have come earlier, but I am kind of confused about these MUST be true questions.

Here, if 3x/y is a prime number greater than 2 then x and y should always be equal so that they can cancel out. We cant have any other factor of 3x/y!!

There are other possibilities here: 3 might be a factor of y, and might therefore cancel in the fraction, leaving us with a prime that comes from the factors of x. For example, if x = 10, and y = 6, then 3x/y = 5. So we can see that none of I, II, or III need to be true.
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what about the case x=y? if x=y then x will cancel Y and answer will be 3, which is greater than 2 and it is prime number

IanStewart wrote:

Economist wrote:

If y ≠ 3 and 3x/y is a prime integer greater than 2, which of the following must be true? Ⅰ. x = yⅡ. y = 1Ⅲ. x and y are prime integers.(A) None(B) Ⅰ only(C) Ⅱonly(D) Ⅲonly(E) Ⅰand Ⅲ

Guys, I am sure this might have come earlier, but I am kind of confused about these MUST be true questions.

Here, if 3x/y is a prime number greater than 2 then x and y should always be equal so that they can cancel out. We cant have any other factor of 3x/y!!

There are other possibilities here: 3 might be a factor of y, and might therefore cancel in the fraction, leaving us with a prime that comes from the factors of x. For example, if x = 10, and y = 6, then 3x/y = 5. So we can see that none of I, II, or III need to be true.

Re: If y 3 and 3x/y is a prime integer greater than 2, which of
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11 Sep 2013, 11:51

1

1

Tricky question. Took 1.50min to solve it.

But this is what I did.

1st Statement: From first looking at the expression, 'x=y' is the easiest way to have a Prime Integer greater > 2 (3 in this case) from the original question stem. Now we must ask ourselves, is there anyway that this number is a prime number greater than 2 and different from 3? Say for example 5. First look at the denominator, to have 5 as the answer we need to get rid of the 3 so 'y=3', could be an option. Then if 'x = 5, we have that the expression is in fact 5.

So x/y = 5/3 could be an option.

2nd Statement: Does 'y=1" ? We just found out that 'y=3' is an option so this one is out.

3rd Statement: This is a bit more difficult. We need to ask ourselves again, do they both have to be prime integers? Let's start with the denominator, we used 'y=3' in the last example but 'y' could be in fact any multiple of 3, lets say we picked 6. Now, to have '5' (Prime>2) as an answer we could use 10 in the numerator. Since both 'x' and 'y' are 10 and 6 they don't both have to be prime numbers.

Re: If y 3 and 3x/y is a prime integer greater than 2, which of
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11 Sep 2013, 12:06

jlgdr wrote:

Tricky question. Took 1.50min to solve it.

But this is what I did.

1st Statement: From first looking at the expression, 'x=y' is the easiest way to have a Prime Integer greater > 2 (3 in this case) from the original question stem. Now we must ask ourselves, is there anyway that this number is a prime number greater than 2 and different from 3? Say for example 5. First look at the denominator, to have 5 as the answer we need to get rid of the 3 so 'y=3', could be an option. Then if 'x = 5, we have that the expression is in fact 5.

So x/y = 5/3 could be an option.

2nd Statement: Does 'y=1" ? We just found out that 'y=3' is an option so this one is out.

3rd Statement: This is a bit more difficult. We need to ask ourselves again, do they both have to be prime integers? Let's start with the denominator, we used 'y=3' in the last example but 'y' could be in fact any multiple of 3, lets say we picked 6. Now, to have '5' (Prime>2) as an answer we could use 10 in the numerator. Since both 'x' and 'y' are 10 and 6 they don't both have to be prime numbers.

So answer is (a) None

The only issue with your response is the prompt explicitly says that y≠3

Re: If y 3 and 3x/y is a prime integer greater than 2, which of
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11 Sep 2013, 12:36

2

Nwsmith11 wrote:

jlgdr wrote:

Tricky question. Took 1.50min to solve it.

But this is what I did.

1st Statement: From first looking at the expression, 'x=y' is the easiest way to have a Prime Integer greater > 2 (3 in this case) from the original question stem. Now we must ask ourselves, is there anyway that this number is a prime number greater than 2 and different from 3? Say for example 5. First look at the denominator, to have 5 as the answer we need to get rid of the 3 so 'y=3', could be an option. Then if 'x = 5, we have that the expression is in fact 5.

So x/y = 5/3 could be an option.

2nd Statement: Does 'y=1" ? We just found out that 'y=3' is an option so this one is out.

3rd Statement: This is a bit more difficult. We need to ask ourselves again, do they both have to be prime integers? Let's start with the denominator, we used 'y=3' in the last example but 'y' could be in fact any multiple of 3, lets say we picked 6. Now, to have '5' (Prime>2) as an answer we could use 10 in the numerator. Since both 'x' and 'y' are 10 and 6 they don't both have to be prime numbers.

So answer is (a) None

The only issue with your response is the prompt explicitly says that y≠3

You are right appologies, my bad.

So we could just use x=10 and y=6 for all the Statements and there we go.

Re: If y 3 and 3x/y is a prime integer greater than 2, which of
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19 Jul 2014, 06:25

Economist wrote:

If y ≠ 3 and 3x/y is a prime integer greater than 2, which of the following must be true?

I. x = yII. y = 1III. x and y are prime integers.

(A) None(B) I only(C) II only(D) III only(E) I and III

Guys, I am sure this might have come earlier, but I am kind of confused about these MUST be true questions.

Here, if 3x/y is a prime number greater than 2 then x and y should always be equal so that they can cancel out. We cant have any other factor of 3x/y!!

Must be true should hold in all the cases

3x/y can be = 3 in this case, Option A) and Option B) comes. It doesn't satisfy Option C) as x= y = 1 is a possibilityIf 3x/y = 5, in this case, Option A) and Option B) goes out of the way and it satisfies option C) Hence None.
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Re: If y 3 and 3x/y is a prime integer greater than 2, which of &nbs
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26 Jun 2018, 04:02